In order to create three-dimensional images or mappings of objects, one often uses techniques of optical sectioning. A so-called optical section is an image that contains information from a certain range of depth. Therefore, an optical system for the generation of images of optical sections performs selective imaging of those object details which are within the focal plane, while object details outside the focal plane are suppressed in the optical section image. By means of recording a series of optical section images located at different focal positions one can scan a three-dimensional (3D) object, step by step. Thus a three-dimensional representation of an object or its topography can be formed.
Confocal imaging is commonly used for microscopy due to its ability to provide optical sectioning, improved contrast, and high-image resolution (R. H. Webb, “Confocal optical microscopy,” Rep. Prog. Phys. 59, 427-471, 1996). One of the first methods for the generation of optical section images was the confocal microscope described in U.S. Pat. No. 3,013,467 entitled “Microscopy Apparatus”, which was issued to Marvin Minsky in 1961. Here the imaging of details from outside the focal plane is suppressed by an arrangement of confocal pinholes.
The concept of confocal microscopy was already developed by Minsky in 1955, but found widespread use in biology only a few decades later. The reason for this delay is probably due to technological limitations at that time, as confocal imaging requires scanning over the entire imaged target (M. Minsky, “Memoir on inventing the confocal scanning microscope,” Scanning 10, 128-138, 1988, and W. B. Amos and J. G. White, “How the confocal laser scanning microscope entered biological research,” Biol. Cell. 95(6), 335-342, 2003). Though confocal holographic systems that do not require scanning had been developed (P.-C. Sun and E. N. Leith, “Broad-source image plane holography as a confocal imaging process,” Appl. Opt. 33, 597-602, 1994), they are unfortunately not suitable for fluorescence imaging (R. Chmelík and Z. Harna, “Parallel-mode confocal microscope,” Opt. Eng. 38(10), 1635-1639, Oct. 1, 1999), which is commonly practiced in microscopy for biological applications.
In the recent years, a team of scientists from Ben-Gurion University (BGU) in Israel and Johns Hopkins University (JHU) in Baltimore, Md. have developed a technology, which may enable cheaper, faster, and more accurate three-dimensional imaging. The technology is named “Fresnel incoherent correlation holography” or “FINCH” for short, and it may be used in a broad range of medical applications, such as endoscopy, ophthalmology, CT scanning, X-ray imaging and ultrasounds (J. Rosen, and G. Brooker, “Digital spatially incoherent Fresnel holography,” Opt. Lett. 32, 912-914, 2007).
Fresnel incoherent correlation holography (FINCH) offers resolutions beyond the Rayleigh limit and is readily suitable for fluorescence microscopy (J. Rosen, N. Siegel, and G. Brooker, “Theoretical and experimental demonstration of resolution beyond the Rayleigh limit by FINCH fluorescence microscopic imaging,” Opt. Express 19, 26249-26268 2011). Yet, it lacks the optical sectioning capabilities that are most important for the imaging of thick objects. Therefore a novel confocal configuration of FINCH, capable of optical sectioning, is required.
It is an object of the present invention to provide a FINCH based method that is capable of sectioning any desired plane out of 3D object distribution.
It is another object of the present invention to provide a novel confocal microscope device that is capable of suppressing out-of-focus information from recorded holograms.
It is yet another object of the present invention to provide an optical sectioning method, using a phase pinhole, suitable for various holography systems (coherent and incoherent) as well as for non-holographic imaging systems.
Other objects and advantages of the invention will become apparent as the description proceeds.